Ensure NOAH-OWP-Modular can be built manually

[program--]

This PR resolves #730 by ensuring iso_c_fortran_bmi is part of the NOAH-OWP-Modular build when it is built manually. To ensure NOAH-OWP-Modular is built with NGen support, when configuring, the CMake option -DNGEN_IS_MAIN_PROJECT must be set to ON.

Changes

• Add iso_c_fortran_bmi as a dependent CMake subdirectory to the NOAH-OWP-Modular build.

Checklist

• PR has an informative and human-readable title
• Changes are limited to a single goal (no scope creep)
• Code can be automatically merged (no conflicts)
• Code follows project standards (link if applicable)
• Passes all existing automated tests
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future todos are captured in comments
• Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)
• Reviewers requested with the Reviewers tool ➡️

Target Environment support

• Linux
• macOS

[stcui007]

I was able build the build the noah-owp-modular libsurfacebmi.so successfully without any error. So it looks like the fix works.